This invention relates to objectives such as used on cameras or other optical equipment, for forming a real image on photographic film or other suitable receiving surface. The object of the invention is to produce what may be regarded as a new species of extremely high speed wide angle objective, with relatively long back focus so that there is ample space for swinging a reflex mirror if it is desired to use the objective with a single lens reflex camera. A high quality image is produced, with a usable diameter of the entrance pupil which is greater than 0.73 times the equivalent focal length of the entire lens system.
Reference is made to German Pat. Nos. 1,187,393, published on Feb. 18, 1965, and 1,250,153, published on Sept. 14, 1967, both granted for inventions of Erhard Glatzel, one of the joint inventors of the present U.S. application. The present invention may be regarded as an improvement on the lenses disclosed in these German patents.